Strange things exist 13,000 feet below the ocean surface, such as the lumps of the metal manganese that slowly accrete like pearls along the deep seafloor. In certain places, especially in the Pacific, the spherical clumps of varying diameter form vast fields. Some of these metallic nodules, researchers found while combing the Atlantic seabed in 2015, may reach the size of bowling balls.
Since the 1970s, a few enterprising miners have considered harvesting the manganese balls; the United Nations approved the first deep-sea prospecting permits in 2014. Too brittle to be of much structural use alone, manganese when mixed with steel forms an alloy strong enough for prison bars or rifle barrels. The deep sea nodules contain other valuable elements, too, such as cobalt or zinc.
In the Atlantic, removing a few of the manganese balls did not seem to disturb the deep sea inhabitants — because there were no inhabitants to be disturbed. “At this station, very few organisms were found in the nets which captured the manganese nodules,” said University of Hamburg’s Angelika Brandt, part of the team that discovered the large Atlantic manganese nodule field, in a 2015 news release. “It is quite possible that living creatures find the immediate vicinity of the nodules quite inhospitable.”
But new research in the journal Current Biology indicates that not all of these manganese nodule fields are as barren. In fact, remote video surveys conducted between 2011 and 2016, off the Hawaiian Archipelago and in the Peru Basin to the south of the Gal?pagos Islands, found several charming residents: the ghost octopods, also called the deep-sea incirrate octopods.
The ghost octopods’ existence was only recently announced. Explorers with the National Oceanic and Atmospheric Administration’s Okeanos team discovered the creatures deep in the ocean, as The Washington Post reported in March.
“This animal was particularly unusual because it lacked the pigment cells, called chromatophores, typical of most cephalopods, and it did not seem very muscular,” wrote NOAA’s Michael Vecchione in a news release announcing the discovery of the octopod. “This resulted in a ghostlike appearance, leading to a comment on social media that it should be called Casper, like the friendly cartoon ghost.” The animal was “almost certainly” a species heretofore unknown to science, he said, and may even belong to a new genus.
In the new study, a team of German and American scientists led by the Helmholtz Center for Polar and Marine Research observed Casper-type octopods living among the manganese nodes.
“The video footage indicates that the animals have cleaned the seabed around the nodules,” said study co-author and Helmholtz Center evolutionary ecologist Henk-Jan Hoving in a statement. “It probably looks like that because the animals have been filmed using their arms to dig into the sediment around the nodules,” likely in search of food.
The Pacific octopods also displayed a particular egg-laying behavior. The scientists witnessed two animals clinging to the stalks of dead sea sponges, which in turn were anchored to manganese nodes. Suspended above the muddy sea bottom, the mother octopods had a stable place to guard their clutches.
“The brooding behavior of the octopods we observed suggests that, like the sponges, they may also be susceptible to habitat loss following the removal of nodule fields and crusts by commercial exploitation,” the scientists concluded in their paper.
In other words, the biologists worry that should miners harvest the manganese rocks, Casper will have no place to lay her eggs.
